My 6 yr old propane hot water heater doesn't ignite reliably. The pilot is on, there is plenty of propane, the exhaust blower is working fine. The igniter even works fine when I power cycle the unit.
Symptom is: Once every couple of weeks, we notice the water is only lukewarm. I go downstairs to the water heater, and find the exhaust blower going, the pilot on, but no ignition of main burner. Seems like it must have been in that mode for hours. I think the thermostat must be going bad. When I unplug AC power to the unit, and replug, the igniter will ignite the main burner and I am OK again for another week or so, until the same symptom reappears.
Any ideas? Bad thermostat? Or do you think it is a faulty gas valve?